Gas Chromatographic Determination of Fatty Acids and Sterols in Orange Juice

Abstract

A gas chromatographic (GC) method has been developed for the simultaneous quantitation of fatty acids and sterols in orange juice, using a bonded phase fused silica capillary column of intermediate polarity, splitless automatic injection, and flame ionization detection. Sample preparation has been simplified by using 1 g C-18 adsorbent in a disposable minicolumn to extract 2 mL orange juice. Methylation of fatty acids and silylation of the sterols were carried out in the eluted extract (low polarity lipid fraction). The method precision was 7%; recoveries ranged from 83 to 113%. The precision of the injection technique was 2%. Seven major fatty acids and 5 sterols in orange juice were quantitated by the GC method and identified by GC/mass spectrometry. Quantitative data for several orange juice samples indicated that the levels of the compounds of interest were in the 1.3-72.0 mg/L range. The results demonstrate that bonded phase fused silica capillary GC has great versatility and potential for the quantitative determination of fatty acids and sterols.